In an antibody molecule, there are two heavy chains and two light chains. Each heavy chain and each light chain has at its N-terminal end a variable domain. Each variable domain is composed of four framework regions (FRs) alternating with three complementarily determining regions (CDRs). The residues in the variable domains are conventionally numbered according to a system devised by Kabat et al. This system is set forth in Kabat et al., 1987, in Sequences of Proteins of Immunological Interest, US Department of Health and Human Services, NIH, USA (hereafter “Kabat et al. (supra)”). This numbering system is used in the present specification except where otherwise indicated.
The Kabat residue designations do not always correspond directly with the linear numbering of the amino acid residues. The actual linear amino acid sequence may contain fewer or additional amino acids than in the strict Kabat numbering corresponding to a shortening of, or insertion into, a structural component, whether framework or CDR, of the basic variable domain structure. The correct Kabat numbering of residues may be determined for a given antibody by alignment of residues of homology in the sequence of the antibody with a “standard” Kabat numbered sequence.
The CDRs of the heavy chain variable domain are located at residues 31-335 (CDRHI), residues 50-65 (CDRH2) and residues 95-102 (CDRH3) according to the Kabat numbering.
The CDRs of the light chain variable domain are located at residues 24-34 (CDRL1), residues 50-56 (CDRL2) and residues 89-97 (CDRL3) according to the Kabat numbering.
Construction of CDR-grafted antibodies is described in European Patent Application EP-A-0239400, which discloses a process in which the CDRs of a mouse monoclonal antibody are grafted onto the framework regions of the variable domains of a. human immunoglobulin by site directed mutagenesis using long. oligonucleotides. The CDRs determine the antigen binding specificity of antibodies and are relatively short peptide sequences carried on the framework regions of the variable domains.
The earliest work on humanising monoclonal antibodies by CDR-grafting was carried out on monoclonal antibodies recognising synthetic antigens, such as NP. However, examples in which a mouse monoclonal antibody recognising lysozyme and a rat monoclonal antibody recognising an antigen on human T-cells were humanised by CDR-grafting have been described by Verhoeyen et al. (Science, 239, 1534-1536, 1988) and Riechmann et al. (Nature, 332, 323-324, 1988), respectively.
Riechmann et al., found that the transfer of the CDRs alone (as defined by Kabat (Kabat et al. (supra) and Wu et al., J. Exp. Med., 132, 211-250, 1970)) was not sufficient to provide satisfactory antigen binding activity in the CDR-grafted product. It was found that a number of framework residues have to be altered so that they correspond to those of the donor framework region. Proposed criteria for selecting which framework residues need to be altered are described in International Patent Application WO 90/07861.
A number of reviews discussing CDR-grafted antibodies have been published, including Vaughan et al. (Nature Biotechnology, 16, 535-539, 1998).
TNFα is a pro-inflammatory cytokine that is released by and interacts with cells of the immune system. Thus, TNFα is released by macrophages that have been activated by lipopolysaccharides (LPS) of gram negative bacteria. As such, TNFα appears to be an endogenous mediator of central importance involved in the development and pathogenesis of endotoxic shock associated with bacterial sepsis. TNFα has also been shown to be up-regulated in a number of human diseases, including chronic diseases such as rheumatoid arthritis, Crohn's disease, ulcerative colitis, and multiple sclerosis. Mice transgenic for human TNFα produce high levels of TNFα constitutively and develop a spontaneous, destructive polyarthritis resembling rheumatoid arthritis (Kaffer et al., EMBO J., 10, 4025 4031, 1991). TNFα is therefore referred to as a pro-inflammatory cytokine.
Monoclonal antibodies against TNFα have been described in the prior art. Meager et al., (Hybridoma, 6, 305-311, 1987) describe murine monoclonal antibodies against recombinant TNFα. Fendly et al., (Hybridoma, 6, 359-370, 1987) describe the use of murine monoclonal antibodies against recombinant TNFα in defining neutralising epitopes on TNF. Shimamoto et al., (Immunology Letters, 17, 311-318, 1988) describe the use of murine monoclonal antibodies against TNF7 and their use in preventing endotoxic shock in mice. Furthermore, in International Patent Application WO 92/11383, recombinant antibodies, including CDR-grafted antibodies, specific for TNFα are disclosed. Rankin et al., (British J. Rheumatology, 34, 334-342, 1995) describe the use of such CDR-grafted antibodies in the treatment of rheumatoid arthritis. U.S. Pat. No. 5,919,452 discloses anti-TNF chimeric antibodies and their use in treating pathologies associated with the presence of 5 TNF.
Antibodies to TNFα have been proposed for the prophylaxis and treatment of endotoxic shock (Beutler et al., Science, 234, 470-474, 1985). Bodmer et al., (Critical Care Medicine, 21, S441-S446, 1993) and Wherry et al., (Critical Care Medicine, 21, S436S440, 1993) discuss the therapeutic potential of anti-TNFα antibodies in the treatment of septic shock. The use of anti-TNFα antibodies in the treatment of septic shock is also discussed by Kirschenbaum et al., (Critical Care Medicine, 26, 1625-1626, 1998). Collagen-induced arthritis can be treated effectively using an anti-TNFα monoclonal antibody (Williams et al. (PNAS-USA, 89, 9784-9788, 1992)).
Increased levels of TNFα are found in both the synovial fluid and peripheral blood of patients suffering from rheumatoid arthritis. When TNFα blocking agents are administered to patients suffering from rheumatoid arthritis, they reduce inflammation, improve symptoms, and retard joint damage (McKown et al. (Arthritis Rheum., 42, 1204-1208, 1999).
The use of anti-TNFα antibodies in the treatment of rheumatoid arthritis and 20 Crohn's disease is discussed in Feldman et al., (Transplantation Proceedings, 30, 41264127, 1998), Adorini et al., (Trends in Immunology Today, 18, 209-211, 1997) and in Feldman et al., (Advances in Immunology, 64, 283-350, 1997). The antibodies to TNFα used in such treatments are generally chimeric antibodies, such as those described in U.S. Pat. No. 5,919,452.
Two TNFα blocking products are currently licensed for the treatment of rheumatoid arthritis. The first, called etanercept, is marketed by Immunex Corporation as Enbrel™. It is a recombinant fusion protein comprising two p75 soluble TNF-receptor domains linked to the Fc portion of a human immunoglobulin. The second, called infliximab, is marketed by Centocor Corporation as Remicade™. It is a chimeric antibody having murine anti-TNFα variable domains and human IgGI constant domains.
The prior art recombinant anti-TNFα antibody molecules generally have a reduced affinity for TNFα compared to the antibodies from which the variable regions or CDRs are derived, generally have to be produced in mammalian cells and are expensive to manufacture. Prior art anti-TNFα, antibodies are described in Stephens et al., (Immunology, 85, 668-674, 1995), GB-A-2 246 570 and GB-A-2 297 145.
WO 01/94585 describes antibody molecules having high affinity for TNFα and low immunogenicity in humans, which can be used repeatedly and produced easily and efficiently, to treat chronic inflammatory diseases.